The invention relates to a pneumatic motor, in which a rotor driven by compressed air rotates in a cylindrical motor sleeve.
An example of such a pneumatic motor is a known vane motor as described, for example, in DE 295 10 799.5. In such a vane motor, a rotor is arranged eccentrically in a cylinder sleeve. Longitudinal slots, in which vanes are accommodated, are located in he rotor body. However, the invention is in no way restricted to vane motors. It can also be applied, for example, to gear motors which are operated with compressed air and in which the rotor consists of a gear pair.
Compressed air fed to the vane motor passes into chambers formed between the vanes. The compressed air drives the motor, so that the rotor starts to rotate in the cylinder. In this case, the vanes may be pressed outwards by springs and with increasing rotary speed under the effect of the centrifugal force, so that they bear against the cylinder in a sealing manner and thus form chambers.
On account of the frictional contact between the vanes and the inner wall of the cylinder, the motor must be lubricated during operation. The conventional method for this purpose provides for oil to be added to the compressed operating air, so that this oil is distributed in the entire motor space and leads to uniform lubrication of the motor.
However, lubrication by compressed air containing oil has proved to be disadvantageous in practice. On the one hand, the oil is transported out of the motor again with the compressed air, a factor which leads to disposal problems. In particular, however, during use under difficult conditions (e.g. in the offshore sector) compressed air enriched with sufficient oil is often not available or the oil reservoirs are not sufficiently refilled.
The object of the present invention is therefore to improve a motor of the said type to the effect that lubrication with compressed operating air containing oil is no longer necessary.
This object is achieved by the present invention. Accordingly, provisions are consequently made for cavities that accommodate a lubricant to be located in the rotor and for these cavities to be connected to the interior space of the cylinder. During operation of the motor, the preferably pasty lubricant accommodated in the cavities inside the rotor is conveyed by the effect of the centrifugal force (during rotation of the rotor) out of the cavities via the connecting paths into the cylinder. In the case of a vane motor, the vanes then provide for the uniform distribution of the lubricant on the inner wall of the cylinder.
In the process, such a quantity of lubricant is preferably fed into the cavities that the motor is sufficiently lubricated for a long time without refilling. In the ideal case, the supply quantity and the outflow quantity, by suitable configuration of the cavities and openings or connecting paths, is selected in such a way that the motor contains a quantity of lubricant which is sufficient for its entire service life.
It is especially advantageous that no additional movable parts are necessary for the lubrication.
In an advantageous development of the invention, the cavities are in each case closed by a porous diaphragm or the like. In this way, accurate metering, which can be predetermined by the type of diaphragm, of the outflow of lubricant is achieved. The lubricant trickles through the porous material only in very small quantities, which, however, are sufficient for the lubrication.
In another development of the invention, provision is made for the cavities to be designed as at least one longitudinal bore in the rotor. Radial bores are likewise possible, but it is simpler with axial bores to keep the outflow quantity of lubricant slight. The longitudinal bores are preferably to be made between two vanes. They may be filled with lubricant over their entire length, so that a sufficiently large reservoir is formed. The porous diaphragm, with which the ends of the bore are in each case preferably closed off, is made, for example, of a porous plastic material of a few millimeters thickness, depending on the size of the rotor.
In a development of the invention, the axial cavities are to be arranged symmetrically around the axis of rotation of the rotor. This is especially advantageous because no unbalance of the rotor develops in a symmetrical arrangement.
According to claim 5, the invention can also be applied to compressed-air-driven gear motors. Radial bores may be expedient in order to lubricate the tooth flanks.